Sextant by David Barrie.

[ollypenrice]

While we now regard astronomical research as being conducted in the pursuit of pure knowledge, the great national observatories were usually founded and funded in order to improve timekeeping and maritime navigation. David Barrie's book https://www.amazon.com/Sextant-Voyage-Guided-Mapped-Worlds/dp/0007516568 is proving to be an excellent read based around his own transatlantic crossing as a young man and on the history of the Sextant. On these two hooks he hangs an engrossing history of navigation.

Of particular interest is the counterbalance he provides to Dava Sobel's book Longitude in which Harrison's chronometer provided, almost at a stroke , the complete solution to the longitude problem. Barrie and other historians of the sea whom I've read suggest otherwise: that the lunar distances method (measuring with a sextant) was a necessary additional method, particularly after long periods at sea when chronometers accumulated error. The two methods co-existed for decades, it seems.

The astronomical content of this book is high.

Recommended.

Olly

[Tiki]

18 hours ago, ollypenrice said:

The two methods co-existed for decades, it seems.

Yes. The lunar distance tables were published up until about 1906, being made redundant I suppose by reliable chronometers. Slocum rather famously circumnavigated the world in the 1890's with an 'old tin clock with only one hand' which had to be boiled whenever it stuck!! 

A competent navigator with a sextant and chronometer is reckoned to be able to fix his position within about a mile. Lunar distance methods are much more sensitive to error and yield fixes to within about 15ish miles.

[Nyctimene]

On 24.2.2018 at 08:24, Tiki said:

Slocum rather famously circumnavigated the world in the 1890's with an 'old tin clock with only one hand' which had to be boiled whenever it stuck!! 

Boiled in oil.... (IIRC my former readings).

Stephan

[ollypenrice]

Sadly the book leaves us feeling that the less said about Slocum the better.

Olly

[ollypenrice]

Of vaguely related interest,

https://www.theguardian.com/australia-news/2018/mar/06/worlds-oldest-message-bottle-western-australia-wedge-island?CMP=fb_gu

Olly